This invention relates to fluid pressure-operated braking systems for motor vehicles and particularly to dual circuit systems where each circuit serves a rear axle brake and at least one front axle brake.
The application of load sensing modulating means to such systems has heretofore involved the insertion of a load sensing valve in each rear brake circuit. The possibility of using a load sensing valve in one circuit only and relaying the modulated pressure to the other circuit has received consideration, but use of a simple relay valve for this purpose would not meet safety regulations as in such circumstances a failure in the circuit embodying the load sensing valve could result in both circuits being rendered inoperative.